Sunil Lilhare
Ansys Employee

Hello, in general if the mesh is good and simulation setup is correct, then the residuals fall below prescribed value after some iterations. However, for steady state simulations, sometimes the residuals drop initially and then fluctuates about mean value. In such cases, additional report definition plots should also be monitored.

Additionally, if it is inferred that the convergence has been reached, then proper mass or energy balance should also be checked.

For such cases where residuals and report definition plots fluctuates about the mean value and do not fall down for any number of further iterations performed, the simulation should be continued in the transient mode for better accuracy.

In the shared images it looks like the residuals are falling, so the iterations should be continued further.

For detailed information on how to select proper y plus values, please have a look at the Lesson 2 of the AIS course on Turbulence Modelling in Ansys Fluent whose link is given below.

Turbulence Modeling in Ansys Fluent | Ansys Innovation Courses